# How do I convert a Normally Open switch to normally closed?

#### ssr215

Joined May 15, 2021
12
I want to make a "Reset" button for my repurposed ATX PSU that cuts the jump between PS_ON and GND when pressed (to reset protection mechanisms). How do I do so?

Joined Jul 18, 2013
25,010
Purchase a N.C. PB ?

#### djsfantasi

Joined Apr 11, 2010
8,258
1) use a relay

#### ssr215

Joined May 15, 2021
12
Purchase a N.C. PB ?
EDIT: Purpose for the circuit is that turning off and on the PSU's switch doesn't reset protection mechanisms.

Joined Jul 18, 2013
25,010
Not completely sure what you want achieve?

#### ssr215

Joined May 15, 2021
12
Not completely sure what you want achieve?
I want to keep the PS_ON and GND always shorted and only disconnect them to reset protection mechanisms. (My PSU has a switch).

#### Ya’akov

Joined Jan 27, 2019
5,518
Why would a normally closed pushbutton switch not work?

#### ssr215

Joined May 15, 2021
12
Why would a normally closed pushbutton switch not work?
I only have normally open buttons.

#### Ya’akov

Joined Jan 27, 2019
5,518
Do you have any relays?

#### ssr215

Joined May 15, 2021
12

#### Ya’akov

Joined Jan 27, 2019
5,518
Then wire the NO pushbutton to the coil of the relay and use the NC contact on the relay to maintain the PS_ON to GND connection. When you press the button and energize the relay, it will break the circuit and reset it.

#### xox

Joined Sep 8, 2017
674
If you're looking for a "switch" that is also very low in power consumption you can use either a comparator or an op amp (single-supply configuration).

It's a bit of a hack of course, but I've used it many times without any problems. And again, the cost of powering the circuit is miniscule. Just keep in mind that the output should be consider a control signal only. Powering higher amperage loads is NOT recommended.

#### djsfantasi

Joined Apr 11, 2010
8,258
I only have normally open buttons.
Where are you from? A NC Push Button costs less than $2. With shipping, it’s less than$10.

Or you can use a relay, if you have one rated for the supply voltage and switched current.

Both suggestions have been mentioned many times.

#### BobaMosfet

Joined Jul 1, 2009
1,951
I want to make a "Reset" button for my repurposed ATX PSU that cuts the jump between PS_ON and GND when pressed (to reset protection mechanisms). How do I do so?
inverter gate.

#### old_beggar

Joined Jan 29, 2021
39
Surely a transistor and 2 resistors will do the same thing? If I understand the requirement, PS_ON needs to be kept grounded except when a reset is necessary. ssr215 do you have any transistors? A BD139 or similar? Within reason, anything will do.

#### Ya’akov

Joined Jan 27, 2019
5,518
I just realized the fatal flaw in all proposals except purchasing the correct switch: the PS is not available to power anything.

#### Ian0

Joined Aug 7, 2020
4,865
Use a spring to keep the N/O switch pressed. Then add a lever to pull the pushbutton upwards against the spring.
Hint: a N/C switch is probably cheaper than a spring.

#### Ya’akov

Joined Jan 27, 2019
5,518
Use a spring to keep the N/O switch pressed. Then add a lever to pull the pushbutton upwards against the spring.
Hint: a N/C switch is probably cheaper than a spring.
A piece of duct tape can hold it down.

#### Ian0

Joined Aug 7, 2020
4,865
A piece of duct tape can hold it down.
But won't it lose its stickiness after a few operations?

#### Ya’akov

Joined Jan 27, 2019
5,518
But won't it lose its stickiness after a few operations?
Only if you use the cheap stuff! But the way I see it, if we are going janky we might as well go full jank.